Oil pump controlling system of hybrid vehicle and method thereof

ABSTRACT

The present invention relates to an oil pump control apparatus of a hybrid vehicle that controls an oil pump according to a demand of an output torque and oil temperature, and a method thereof. A oil pump control method includes controlling hydraulic line pressure by operating a oil pump at a maximum power if a starting demand for a hybrid vehicle is detected, calculating a viscosity to correspond to an oil temperature in an engine stop mode and controlling a rotation speed of the oil pump at a low power, and calculating a viscosity according to a variation of a line pressure in a driving mode and controlling the rotation speed of the electric oil pump in either a low power, a middle power, and a high power state.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2010-0124357 filed in the Korean IntellectualProperty Office on Dec. 7, 2010, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a hybrid vehicle. More particularly,the present invention relates to an oil pump control apparatus of ahybrid vehicle that controls an oil pump according to a demand foroutput torque and oil temperature, and a method thereof.

(b) Description of the Related Art

Demand for an environmentally-friendly vehicle has increased byreinforcement of exhaust gas regulations and enhancement of fuelefficiency concerns, and hybrid vehicles have been spotlighted as arealistic alternative.

A hybrid vehicle can be distinguished from a fuel cell vehicle and anelectric vehicle in a narrow sense, and the hybrid vehicle in thisspecification can include a fuel cell vehicle and an electric vehicle ina broad sense and can designate a vehicle that has an engine and atleast one high voltage battery and a motor that is operated by thebattery. The engine and a motor are applied to a hybrid vehicle as powersources, and are appropriately combined according to driving conditionsto enhance fuel efficiency and to reduce exhaust gas emission.

Hybrid vehicles improve fuel consumption efficiency by combining powerfrom the engine and the motor when the engine and the motor areoperated. Hybrid vehicles adopt a hybrid stop and go (HSG) function toautomatically turn the engine on or off according to a drivingconditions. Additionally, when the hybrid vehicle is in an electricvehicle (EV) mode, the engine may also be turned off to conserve fuel.

As described above, if the engine is turned off, a mechanical oil pumpthat is connected to a crankshaft of the engine to supply an automatictransmission of the vehicle with oil stops operating. Thus, hydraulicpressure is not properly supplied to the automatic transmission and awet engine clutch as it should be. Accordingly, normal line pressure isnot formed in the automatic transmission so that friction elements(clutches and brakes) realizing a forward first speed are released.

Typically, an electric oil pump is disposed in parallel with themechanical oil pump to resolve the above problem in hybrid vehicles.This electric oil pump is configured to be operated independently fromthe engine and thus is typically able to supply the proper hydraulicpressure to the automatic transmission and the wet engine clutch.

However, when the engine is turned off by the HSG function, the electricoil pump must rotate at a high speed. Thus, the durability of theseelectric pumps is greatly deteriorated, the current of a battery isexcessively spent, and the battery must be more frequently charged anddischarged, thus affecting the durability of the battery.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY OF THE INVENTION

The present invention provides an oil pump control apparatus for ahybrid vehicle which optimally controls rotation speed of an electricoil pump while at the same time realizing a necessary line pressure.That is, the rotation speed of the electric oil pump is variablycontrolled by selecting necessary power so as to control an electric oilpump according to a line pressure corresponding to an oil temperatureand a demanded torque.

A oil pump control apparatus of a hybrid vehicle may include an enginethat is operated or not operated as a first power source depending on adriving mode and condition, a motor that is operated as a second powersource by a 3-phase AC current supplied from an inverter to transferoutput torque to a transmission and function as a generator to retrievea regeneration energy during deceleration, an engine clutch thatconnects or disconnects the engine with the motor, a first oil pump thatis disposed in a transmission to be connected to the motor, which isoperated by the motor in a condition that the engine is turned off in anEV or HSG mode, and is operated by the engine power transferred from theengine clutch in an HEV mode to create a line pressure, an electric oilpump that is operated in a condition that the engine is turned off in anEV or HSG mode to form a hydraulic pressure in the transmission and theengine clutch, and a hybrid controller that controls the electric oilpump according to a line pressure based on a power (current and voltage)to variably control a rotation speed of the electric oil pump.

In one or more embodiments of the present invention, the hybridcontroller may operate the electric oil pump at maximum power(current×voltage) to create line pressure if a driving signal isdetected. Additionally, the hybrid controller may calculate theviscosity the oil according to the oil temperature in an engine stopmode and operate the electric oil pump at a low power state. Likewise,the hybrid controller may calculate the viscosity of oil in a drivingmode, control an operating speed of the electric oil pump in either alow power, a middle power, or a high power state, and variably controlan operating speed thereof according to the line pressure by adjustingthe electric power appropriately. In performing the above operation, thehybrid controller may use vehicle speed, input torque, gear speed,inhibiter switch position, a line pressure learned value, real rotationspeed, input current, input voltage, on/off operating time of theelectric oil pump, and line pressure to calculate the viscosity of theoil. As a result, the hybrid controller may learn a viscosity of oilaccording to a driving condition to revise a map table for determiningan operating speed of the electric oil pump.

An oil pump control method of a hybrid vehicle may include creating linepressure by operating the electric oil pump at maximum power(current×voltage) if the starting demand for a hybrid vehicle isdetected. Then a viscosity is calculated to correspond to an oiltemperature in an engine stop mode and a rotation speed of the electricoil pump is controlled in a low power state. Alternatively, viscosity iscalculated according to variation of the line pressure in a driving modeand the rotation speed of the electric oil pump in either a low power, amiddle power, or a high power state according to that viscosity.

An operating speed of the electric oil pump may be variably controlledby varying a power for operating the electric oil pump according to theline pressure in a driving mode. A vehicle speed, input torque, gearspeed, inhibiter switch position, a line pressure learned value, realrotation speed, input current, input voltage, on/off duration time ofthe electric oil pump, and line pressure may be used to calculate theviscosity of oil.

As described above, a control signal of an electric oil pump is variedaccording to the line pressure so as to create line pressurecorresponding to a demand torque according to an exemplary embodiment ofthe present invention, wherein the electric oil pump is operated with anecessary power (voltage×current) such that rotation speed of theelectric oil pump is actively controlled, power consumption of a batteryis reduced, and fuel consumption efficiency is improved.

The electric oil pump is operated based on electric power, and rotationspeed of the electric oil pump is actively varied corresponding to theline pressure according to an exemplary embodiment of the presentinvention such that a target pressure is securely realized to offeroptimized control.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing schematically showing an oil pump control apparatusof a hybrid vehicle according to an exemplary embodiment of the presentinvention.

FIG. 2 is a flowchart showing procedures for oil pump control of ahybrid vehicle according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, in the following detailed description, only certainexemplary embodiments of the present invention have been shown anddescribed, simply by way of illustration.

As those skilled in the art would realize, the described embodiments maybe modified in various different ways, all without departing from thespirit or scope of the present invention, and the drawings anddescription are to be regarded as illustrative in nature and notrestrictive.

Note that it is understood that the term “vehicle” or “vehicular” orother similar term as used herein is inclusive of motor vehicles ingeneral such as passenger automobiles including sports utility vehicles(SUV), buses, trucks, various commercial vehicles, watercraft includinga variety of boats and ships, aircraft, and the like, and includeshybrid vehicles, plug-in hybrid electric vehicles, hydrogen-poweredhybrid vehicles and other alternative hybrid vehicles. As referred toherein, a hybrid vehicle is a vehicle that has two or more sources ofpower, for example both gasoline-powered and electric-powered vehicles.

FIG. 1 is a drawing schematically showing an oil pump control apparatusof a hybrid vehicle according to an exemplary embodiment of the presentinvention. Referring to FIG. 1, an exemplary embodiment of the presentinvention includes an engine 100, an HSG 110, an engine clutch 130, amotor 200, a transmission 300, a mechanical oil pump 310, an electricoil pump 400, a hybrid controller 410, an oil pump controller 420, anauxiliary battery 430, an inverter 440, and a main battery 450.

The engine 100 is operated as a first power source in a hybrid vehicle,and is on/off controlled depending during certain driving modes and incertain driving conditions. The engine 100 is turned off in an EV mode,is started in a HEV mode, and is on/off controlled depending on an HSGfunction. The HSG 110 starts or stops the engine 100 depending on theHSG function, and in a case that excess power of the engine 100 exists,the HSG 110 transforms the excess power into an electric voltage/currentand the generated voltage/current is charged to the main battery 450through the inverter 440. The engine clutch 130 is disposed between theengine 100 and the motor 200 to regulate power delivery, and in mostcases a wet type of clutch is applied thereto to be operated by ahydraulic pressure supplied from the first oil pump 310 or the electricoil pump 400.

The motor 200 is a second power source in a hybrid vehicle, and isoperated by a 3-phase AC current supplied from the inverter 440 totransfer output torque thereof to the transmission 300, generate avoltage by retrieving regeneration energy through braking(deceleration), and charge the main battery 450 through the inverter400.

The transmission 300 can be either an automatic transmission or a CVT. Agear ratio thereof is changed according to a demand torque and drivingconditions, and output torque that is added through the engine clutch130 according to a driving mode is varied by the gear ratio to betransferred to a driving wheel.

The first oil pump 310 is disposed in the transmission 300 to beconnected to an output shaft of the motor 200, is operated by the motor200 when the engine 100 is turned off by the EV mode or the HSG functionto create hydraulic pressure, and is operated by torque of the engine100 supplied from the engine clutch 130 to create hydraulic pressure inthe HEV mode. The first oil pump 310 includes a mechanical oil pumpfunction that is operated by the engine 100 to create hydraulic pressureand an electric oil pump function that is operated by the motor 200 tocreate hydraulic pressure.

The electric oil pump 400 is operated when the engine 100 is turned offby the HSG function or the vehicle moves in the EV mode to formhydraulic pressure in the transmission 300 and the engine clutch 130.The hybrid controller 410 operates the electric oil pump (EOP, 400) withmaximum power (current×voltage) to create line pressure, and learns theline pressure so as to be feedback controlled.

That is, the hybrid controller 410 operates the electric oil pump 400 atfull power in the early stages, calculates an oil viscosity so as tocorrespond to an oil temperature in an engine stop mode, and determinespower (current×voltage) for controlling the operating speed of theelectric oil pump 400 to a low power state to control the operatingspeed of the electric oil pump 400.

Also, the hybrid controller 410 calculates an oil viscosity according toline pressure in a driving mode, and determines a power(current×voltage) for controlling the operating speed of the electricoil pump 400 to either a low power, a middle power, and a high powerstate so as to variably control the operating speed of the electric oilpump 400 against a sudden deceleration, a creep condition, etc. Thehybrid controller 410 uses vehicle speed, input torque, gear speed,inhibiter switch position, a line pressure learned value, real rotationspeed, input current, input voltage, on/off operating time of theelectric oil pump 400, and line pressure to calculate the viscosity ofthe oil. The hybrid controller 410 learns the viscosity of theassociated oil according to according to driving conditions to revise amap table for determining an operating speed of the electric oil pump400.

The oil pump controller 420 uses electric power to operate the electricoil pump 400 by control of the hybrid controller 410, and variablycontrols the speed of the electric oil pump 400 according to a linepressure condition. The auxiliary battery 430 provides an electricalload to supply each controller with necessary power. The inverter 440transforms DC voltage supplied from the main battery 450 to 3-phase ACvoltage according to the control of the hybrid controller 410 to controlthe operating torque and speed of the motor 200. The inverter 440charges the main battery 450 with a generated electric power that isformed when the motor 200 functions as a generator. The main battery 450supplies the motor 200 with electric power to assist the output of theengine 100 in the HEV mode and stores the power generated from the motor200.

FIG. 2 is a flowchart showing procedures for oil pump control of ahybrid vehicle according to an exemplary embodiment of the presentinvention. The hybrid controller of the hybrid vehicle according to thepresent invention operates the electric oil pump 400 with maximum power(current×voltage) to quickly form early line pressure if a signal forstarting the engine is detected in step S110, wherein the line pressureformed is learned to be feedback controlled in step S120.

As described above, after the electric oil pump 400 is operated with amaximum load at an initial stage, the oil viscosity is calculated so asto correspond to an oil temperature of the transmission 300, and theelectric oil pump 400 is operated with a low power (current×voltage) inan engine stop mode to control the speed of the electric oil pump 400 instep S130.

Also, if the power is determined to operate the electric oil pump 400 inthe engine stop mode, the oil viscosity is calculated in the drivingmode, the power (current×voltage) for operating the electric oil pump400 is determined as either a low power, a middle power, and a highpower state to control the speed of the electric oil pump 400 against aquick deceleration, a creep condition, etc. in step S140. The vehiclespeed, input torque, gear speed, inhibiter switch position, linepressure learned value, real rotation speed, input current, inputvoltage, on/off operating time of the electric oil pump 400, and linepressure to calculate the viscosity of oil are used to calculate theviscosity in the engine stop mode and the driving mode.

The steps S130 and S140 are repeated until the vehicle stops operating,i.e., an OFF signal is detected, and the map table determining theoperating speed of the electric oil pump 400 can be revised by learningthe viscosity that is calculated according to the driving condition.

Furthermore, the controllers described herein may be embodied asnon-transitory computer readable media on a computer readable mediumcontaining executable program instructions executed by a processor.Examples of the computer readable mediums include, but are not limitedto, flash storage, ROM, RAM, magnetic tapes, floppy disks, and opticaldata storage devices. The computer readable recording medium can also bedistributed in network coupled computer systems so that the computerreadable media is stored and executed in a distributed fashion

Advantageously, the present invention provides an electric oil pumpwhich is actively varied corresponding to line pressure according sothat a target pressure is securely realized to offer optimized while atthe same time allowing for increased durability of both the electricpump and the battery due unnecessary rotational speed.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

DESCRIPTION OF SYMBOLS

-   -   100: engine    -   200: motor    -   300: transmission    -   310: first oil pump    -   400: electric oil pump    -   410: hybrid controller    -   420: oil pump controller    -   440: inverter

1. An oil pump control apparatus of a hybrid vehicle, comprising: anengine operated as a first power source, wherein the engine isconfigured to be turned on and off depending on a driving mode andcondition; a motor that is operated as a second power source by a3-phase AC current supplied from an inverter to transfer output torqueto a transmission and function as a generator to retrieve a regenerationenergy during deceleration; an engine clutch that connects anddisconnects the engine with the motor; a first oil pump disposed in atransmission to be connected to the motor, the first oil pump operatedby the motor when the engine is turned off in an electric vehicle (EV)or hybrid stop and go (HSG) mode, and is operated by the engine powertransferred from the engine clutch in an hybrid electric vehicle (HEV)mode to form a line pressure; an electric oil pump configured to beoperated when the engine is turned off in an EV or HSG mode to form ahydraulic pressure in the transmission and the engine clutch; and ahybrid controller that controls the electric oil pump according to aline pressure based on a required power to variably control a rotationspeed of the electric oil pump.
 2. The oil pump control apparatus ofclaim 1, wherein the hybrid controller operates the electric oil pump atmaximum power (current×voltage) to create line pressure if a drivingsignal is detected.
 3. The oil pump control apparatus of claim 1,wherein the hybrid controller calculates a viscosity of oil according tooil temperature in an engine stop mode and operates the electric oilpump in a low power state according to the calculated viscosity of oil.4. The oil pump control apparatus of claim 1, wherein the hybridcontroller operates the electric oil pump according to an oiltemperature.
 5. The oil pump control apparatus of claim 1, wherein thehybrid controller calculates a viscosity of oil in a driving mode,controls an operating speed of the electric oil pump in either a lowpower, a middle power, or a high power state, and variably controls anoperating speed thereof according to line pressure by adjusting electricpower.
 6. The oil pump control apparatus of claim 4, wherein the hybridcontroller uses a vehicle speed, an input torque, a gear speed, aninhibiter switch position, a line pressure learned value, a realrotation speed, an input current, an input voltage, an on/off operatingtime of the electric oil pump, and a line pressure to calculate theviscosity of the oil.
 7. The oil pump control apparatus of claim 1,wherein the hybrid controller learns a viscosity of oil according to adriving condition in order to revise a map table for determining anoperating speed of the electric oil pump.
 8. An method for controllingan oil pump of a hybrid vehicle, comprising: controlling a line pressureby operating the electric oil pump at a maximum power (current×voltage)in response to a starting demand for a hybrid vehicle being detected;calculating a viscosity to correspond to an oil temperature in an enginestop mode and controlling a rotation speed of the electric oil pump in alow power state; and calculating a viscosity according to a variation inline pressure in a driving mode and controlling a rotation speed of theelectric oil pump in either a low power, a middle power, or a high powerstate.
 9. The oil pump control method of claim 8, wherein an operatingspeed of the electric oil pump is variably controlled by varying a powerfor operating the electric oil pump according to a line pressure in adriving mode.
 10. The oil pump control method of claim 8, wherein avehicle speed, an input torque, a gear speed, an inhibiter switchposition, a line pressure learned value, a real rotation speed, an inputcurrent, an input voltage, an on/off duration time of the electric oilpump, and a line pressure are used to calculate the viscosity of oil.11. An oil pump control apparatus of a hybrid vehicle, comprising: anoil pump configured to be operated when a engine in the hybrid vehicleis turned off to create hydraulic pressure in the transmission and theengine clutch; and a controller configured to control the electric oilpump according to line pressure based on a required power calculated bylearning the current viscosity of oil to variably control a rotationspeed of the oil pump depending upon driving conditions of the hybridvehicle.
 12. The oil pump control apparatus of claim 11, wherein thecontroller operates the oil pump at maximum power to create linepressure if a driving signal is detected.
 13. The oil pump controlapparatus of claim 11, wherein the controller calculates viscosity ofthe oil according to oil temperature in an engine stop mode and operatesthe electric oil pump in a low power state according to the calculatedviscosity of oil.
 14. The oil pump control apparatus of claim 11 whereinthe oil pump is an electric oil pump.
 15. A non-transitory computerreadable medium containing executable program instructions executed by aprocessor, comprising: program instructions control line pressure byoperating an electric oil pump at a maximum power in response to astarting demand for a hybrid vehicle being detected; programinstructions that calculate a viscosity to correspond to an oiltemperature in an engine stop mode and control a rotation speed of theelectric oil pump in a low power state in response to the calculation;and program instructions that calculate a viscosity according to avariation in line pressure in a driving mode and control the rotationspeed of the electric oil pump to either a low power, a middle power, ora high power state.